Polyalkylene glycol polyalkylene polyamine dispersants for lubricant fluids

ABSTRACT

A new class of dispersant compounds and compositions and a series of novel lubricant compositions are disclosed. Polyalkylene glycol succinimides which may be derived from maleic acids and anhydrides are useful as dispersants in, for example, polyglycol base fluids. Lubricating compositions including such dispersant compositions are also described.

United States Patent Hankins et al.

POLYALKYLENE GLYCOL POLYALKYLENE POLYAMINE DISPERSANTS FOR LUBRICANT FLUIDS lnventors: Tad L. Hankins, Fullerton, Calif.;

Ting-l Wang, Cherry Hill, NJ.

Assignee: Atlantic Richfield Company, Philadelphia, Pa.

Filed: June 11, 1973 App]. No.: 368,678

Related U.S. Application Data Continuation-impart of Ser. No. 765,959, Oct, 8, I968, abandoned.

US. Cl. 260/3265 FM; 252/5l.5 A Int. Cl. C07D 27/00 Field of Search 260/3265 FM; 252/515 A [451 July 29,1975

[56] References Cited UNITED STATES PATENTS 3,172,892 3/l965 Le Suer et al. 260/3265 3,458,530 7/1969 Siegel et al 260/3265 FM 3,630,902 12/1971 Coupland et al 260/3265 FM 3,746,645 7/1973 Saito et a] 252/515 A Primary Examiner-Elbert L Roberts Attorney, Agent, or Firm-John Vander Weit, Jr.

12 Claims, No Drawings POLYALKYLENE GLYCOL POLYALKYLENE POLYAMINE DISPERSANTS FOR LUBRICANT FLUIDS This application is a continuation-in-part of application, Ser. No. 765,959, now abandoned.

The present invention relates to chemical compositions and, more particularly, to chemical compositions useful as lubricating fluid additives and to lubricating fluid compositions. Still more particularly, this invention relates to polyalkylene glycol succinimide lubricant additives and methods for making same.

Motor fuel lubricants, such as conventional automobile motor oil or oils designed for special applications, e.g., marine, aircraft and stationary engines, conventionally include oxidation inhibitors and dispersant additives. Viscosity improvers, etc., are also conventionally added to the basic lubricant fluid to provide particular characteristics desired in the end lubricating composition.

Many hydrocarbon-based or hyrocarbon-containing additives are commercially available for use in conventional hydrocarbon lubricating fluids. It is, of course, desirable that any successful additive be soluble in the lubricating fluid at all potential operating or handling conditions. Long chain aliphatic hydrocarbon substituted succinic acid-amine derivatives have been proposed as dispersant additives for hydrocarbon-based lubricant fluids, see US. Pat. No. 3,172,892, for example.

A new class of potentially commerically valuable base lubricating fluids has been developed, however, in which most known dispersant additives are insoluble or have only limited solubility. An example of this new type of lubricant are products commonly referred to as polyglycols, e.g., polypropylene glycol diether polymers. Therefore, it would be advantageous to provide improved dispersant additives for such lubricant fluids.

Accordingly, an object of the present invention is to provide an improved lubricant for use, for example, as crankcase oils and as lubricants generally, which comprise polyglycols, such as polypropylene glycol diether polymer, as a base fluid and an improved sludge disperzsant additive.

A further object of the present invention is to provide an improved dispersant additive comprising polyalkylene glycol succinimides.

An additional object of the present invention is to provide a method for producing improved dispersant additives for use, for example, in polyglycol lubricant fluids. Other objects and advantages of the present invention will become apparent hereinafter.

A new class of compounds, termed polyalkylene glycol succinimides, useful as a dispersant additive in lubricant fluids, e.g., polyglycols, has now been discovered. These compounds are selected from the group consisting of and mixtures thereof, wherein each R and R is independently selected from the group consisting of hydrogen and monovalent hydrocarbonaceous radicals containing less than about 10 carbon atoms, each R and R is independently selected from the group consisting of hydrogen and alkyl containing from 1 to about 10, preferably from 1 to about 4, carbon atoms, each R is independently selected from the group consisting of divalent hydrocarbonaceous radicals containing from 1 to about 3 carbon atoms, n is a positive integer in the range from about 1 to about 100, preferably from about 10 to about 100, and m is a positive integer from about 1 to about 10. Preferably, n is at least 3 times m, and more preferably 11 is from about 5 to about 15 times m.

The present dispersant additive compositions are useful as dispersants in lubricating compositions for use, for example, in automobile engines, aircraft engines, marine engines, stationary engines and the like. These lubricating compositions may comprise a major amount of a base fluid of lubricating viscosity, such as polyglycols which have the following generalized structural formula:

wherein R, R and n are as described previously. In a preferred embodiment, R is methyl and each R is independently selected from the group consisting of alkyl containing from 1 to about 4 carbon atoms, more preferably, methyl. In this preferred embodiment, the base fluid is termed a polypropylene glycol diether polymer. These base fluids are commercially available and may have viscosities ranging from about 50 SUS to about 2,000 SUS, preferably from about 100 SUS to about 1,000 SUS, at 100F. The viscosity index of these base fluids may range from about 30 to about 220, preferably from about to about 200.

The present dispersant additive concentration level may be from about 0.1 percent to about 10 percent, preferably from about 1 percent to about 5 percent, by weight of the total lubricating composition. Conventional oxidation inhibitors may also be added, in an amount sufficient to inhibit the oxidation of the base fluid, for example, in the range from about 0.1 percent to about 5 percent, preferably in the range from about 0.5 percent to about 3 percent, by weight of the total lubricating composition. Many conventional oxidation inhibitors have been found to be successful, for example, 4,4-methylene, bis-2, 6-ditertiary butyl phenol, alkylated phenols, phenyl alphanaphthylamine, and alkylated diphenylamines were found to be successful oxidation inhibiting additives.

The dispersant compositions of the present invention may be obtained by contacting polyalkylene glycol polymer, described hereinafter, with a maleic compound in the amount of from about 0.1 to about 3, preferably from about 0.5 to about 1.5, moles of glycol polymer per mole of maleic compound at conditions.

sufficient to etherify at least a portion of the maleic compound at the carbon-carbon double bond. This etherified product is contacted with a polyalkylene polyamine in the amount of from about 0.1 to about 3, preferably from about 0.5 to about 1.5, moles of polyamine per mole of maleic compound contacted above at conditions sufficient to react at least a'portion of the etherified product with the amine to form the present dispersant compositions.

As noted above, a polyalkylene glycol polymer is contacted with the maleic compound at conditions sufficient to etherify at least a portion of the maleic compound at the carboncarbon double bond. These contacting conditions are not critical to the present invention and may vary over a broad range depending, for example, on the chemical structure of the materials being contacted, the degree of etherification desired and the like variables. Preferably, this contacting takes place at conditions such that both the polyalkylene glycol ether and maleic compound are substantially in the liquid phase. Thus, the contacting pressure is preferably maintained at a level so that a substantial portion of the polyalkylene glycol polmer, maleic compound, etherified product and solvent, if any, is in the liquid phase. Typical contacting pressures range from about 0.] atmosphere to about 50 atmospheres or more, preferably from about 1 atmosphere to about atmospheres. Contacting temperatures in the range from about 25C. to about 250C., preferably from about 150C. to about 225C, may be utilized. This contacting may be carried out for a period of time from about I hour to about 500 hours, preferably from about 10 hours to about 200 hours.

The etherified product prepared, for example, as described above, is contacted with a polyalkylene polyamine under conditions to form the dispersant compositions of the present invention. The conditions at which this contacting occurs are not critical to the present invention and may vary over a broad range. Preferably, this contacting occurs in the liquid phase and, therefore, contacting pressure is preferably maintained so that a substantial amount of the etherified product, polyalkylene polyamine dispersant composition and solvent, if any, is in the liquid phase, for example, in the range from about 0.1 atmospheres to about 50 atmospheres or more, perferably in the range from about 1 atmosphere to about IO atmospheres. Typical contacting temperatures range from about 50C. to about 300C, preferably from about 100C. to about 225C. This contacting may be carried out for a period of time, for example, in the range from about 1 hour to about 100 hours, preferably from about 10 hours to about 50 hours.

In certain instances, it may be advantageous to carry out either one or both of the above-described contactings in the presence of an inert solvent, Le, a solvent which will not materially adversely affect the formation of the etherified product or the dispersant compositions of the present invention. Examples of suitable solvents include paraffmic, cycloparaffinic and aromatic hydrocarbons containing up to about 10 or more carbon atoms per molecule, such as hexane, cyclohexane, octane. benzene, toluene, xylenes and the like. More than one solvent may be used and different solvents may be used for each of the two contactings. When a solvent is used, it is preferred that the solvent comprise at least about percent, more preferably at least about 30 percent, by weight of the total liquid material present during the contacting. The solvent may be removed from either the etherified product or the present dispersant compositions by conventional procedures, e.g., simple or vacuum distillation and the like.

The polyalkylene glycol polymer suitable for use in producing the dispersant compositions of the present invention may be selected from the group consisting of and mixtures thereof, wherein each R and R are independently selected from the group consisting of hydrogen and alkyl containing from I to about 10, preferably from I to about 4, carbon atoms; and n is a positive integer in the range from about 1 to about 100, preferably from about IO to about 100. Typical examples of the alkyl groups from which R and R may be selected include methyl, ethyl, propyl, butyl, hexyl, nonyl, decyl and the like. More preferably, R and R are all methyl groups and n is in the range from about 10 to about 40.

The maleic compound from which the present additives may be derived are selected from the group consisting of R c c o //0 o a eI c on RZC c 0 R212 c OH and mixtures thereof, wherein R and R are independently selected from the group consisting of hydrogen and monovalent hydrocarbonaceous radicals containing less than about 10 carbon atoms. Typical examples of the monovalent hydrocarbonaceous radicals from which R and R may be chosen include alkyl, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, nonyl, and the like; alkenyl such as ethenyl, propenyl, butenyl, hexenyl, nonenyl, and the like; aryl, alkaryl, and alkenaryl such as phenyl, methyl phenyl, ethyl phenyl, ethenyl phenyl, propyl phenyl, propenyl phenyl and the like; aralkyl ane aralkenyl, such as phenyl methyl, phenyl ethyl, phenyl ethenyl, phenyl propyl, phenyl propenyl and the like. Preferably, R and R are selected from the group consisting of hydrogen and alkyl containing from 1 to about 6 carbon atoms. More preferably, R and R are both hydrogen.

The polyalkylene polyamines from which the present additives may be derived are selected from the group consisting of and mixtures thereof, wherein each R is independently selected from the group consisting of divalent hydrocarbonaceous radicals containing from 1 to about 3 carbon atoms; and m is a positive integer from 1 to about l0. Typical examples of the divalent hydrocarbonaceous radicals from which each R may be independently selected include methylene, ethylene, ethenylene, propylene, propenylene, and the like. It is preferred that all R s be the same. More preferably, all R s are selected from the group consisting of ethylene and propylene, in particular, ethylene.

The above-described hydrocarbonaceous radicals may include non-hydrocarbonaceous substituents. Suitable substituents include those which do not materially interfere with the effectiveness, e.g., dispersant properties, of the compositions of the present invention. Typical examples of such non-interferring substituents include OH, NH and the like radicals. Also, the definitions of all the radicals, e.g., R through R and the positive integers, e.g., m and n, given in detail for the reactants, e.g., polyalkylene glycol polmers, maleic compound and polyalkylene polyamine, apply to the corresponding radicals and positive integers described previously in the dispersant compositions of the present invention.

The following examples illustrate more clearly the process of the invention. However, these illustrations are not to be interpreted as specific limitations on the invention.

EXAMPLE I The following example illustrates certain of the advantages of the present invention.

0.1 mole of a polypropylene glycol polymer having the following approximate structure:

Ca o-ca 1cu on wherein n is a positive integer averaging about 25 and 0.1 mole of maleic anhydride were added to a 500 ml. reaction flask equipped with a water-cooled condenser, along with 100 ml. of xylene. The mixture was heated to 80C., then cooled to 74C. After 24 hours, the temperature was increased to reflux. After 68 hours at reflux, the temperature was 155C, after 116 hours the TABLE I temperature was 172C., and after 164 hours the temperature was 201C. At this point, the reaction flask was cooled down.

0.08 mole of triethylenetetramine and mls. of toluene were added to the reaction flask and the mixture was heated to reflux. After 46 hours the temperature was 157C. Moisture coming off from the mixture was collected as the color of the mixture turned to a dark brown. After about 52 hours, the product was vacuum treated at 150C. and 7 mm. Hg. for 4 hours to remove the solvent prior to solubility testing and evaluation for dispersant effectiveness. Infrared analysis and molecular weight determination confirmed the presence of compounds containing both the ether and amide linkages characteristic of the present compounds.

The product of the above processing was blended with a commercially available end-blocked polypropylene glycol diether polymer so that this product amounted to 5 percent by weight of the total composition. The commercially available end-blocked polypropylene glycol diether polymer nominally has a viscosity of 58.3 SUS at 210F., 201 SUS at F., a viscosity index of 161, a pour point of -50F., a flash point of 520F. and a fire point of 565F. The compounded composition was clear with no observable cloudiness or separation. A commercially available oxidation inhibitor was added at a 3 percent level. The resulting composition is useful as an engine lubricant.

Dispersant effectiveness was tested by blending the product of the above processing with a sample of the commerically available end-blocked polypropylene glycol ether described above which had been used in engines used in dynamometer tests. The blend was mixed in a Waring Blender for 5 minutes. The resulting sample was observed for sludge separation. Paper chromatographic spot tests were also used to determine dispersant effectiveness. Data showing the relative effectiveness of the dispersant composition of this invention are given in Table I along with comparative data using other known and experimental dispersant additives.

DISPERSANT TESTS WARING BLENDER, HIGH SPEED 5 MINUTES Code HrS.Sett1i!11 Q Number Conc. Structure 2 5 0 Separation Standard #1 100 Used Lubricant from chassis dynamometer test on Chevrolet 19 72 Standard #2 100 Used Lubricant from chassis dynamometer test on Ford 4 58 H9- 37-5 5 Product of maleic anhydride, polypropylene glycol polymer and 0 2 tricthylenetetramine c0mprising** wherein n is a positive integer averaging about 25.

by structure.

However other unidentified products are also present which, based on the improved results obtained using the compositions of the present invention, also act as clispersants.

TABLE I (Cont d.)

DISPERSANT TESTS WARING BLENDER, HIGH SPEED 5 MINUTES Code Structure Hrs.Settling Number Gone 24 240 Separation 6459-31-53 5 CH CH 4 43 C l-I CHCO CHCH OCI'lCl-l OR CH CO H 649-36-1 5 Tetrapropenylsuccinic anhydride plus triethylenetetramine 3 19* 649-31-7 5 CH. CH. 3 at 8* J 1 72 C ll -CHCO CHCH -(OCliCli OR I CII CO-(NHCH CH fi N11 21 l 5 C H LHCO 17 3O ncn ca cn nacn cn ca na CH CO *Soap like deposit formed on graduate.

649-14-1 5 C H -CHCO NCH CH NHCH CH NH 6lzat l6 ca co C H CHCO CO-CH NCH CH NHCH CH N l ca co C-CHC H 649-19-1 C12ll -CHCO 3 58* ca cn wr CH CO *Soap like deposit formed on graduate.

The significant advantages of the compositions of this invention compared with other dispersants are immediately apparent. The significantly greater effectiveness of a present dispersant composition, as compared with structurally similar compounds, is quite unexpected.

EXAMPLE II The following examples further illustrate the present invention.

0.1 mole of the polypropylene glycol polymer used in Example I and 0.2 moles of maleic anhydride along with 100 ml. of toluene are placed in a stainless steel autoclave equipped with a mechanical stirrer and temperature control means. Nitrogen is used to pressure the autoclave to 100 psi. Means are provided so that the pressure in the autoclave is maintained at 100 psi. The mechanical stirrer is activated and the temperature of the mixture in the autoclave is slowly increased to 175C. and is maintained there for hours. At this point the mixture is cooled. 0.1 mole of diethylenetriamine is added to the mixture in the autoclave and the temperature is again slowly raised to 125C. This temperature is maintained for 15 hours after which time the mixture is cooled. Residual toluene is stripped from the mixture. Infrared analysis and molecular weight determinations confirm the presence in the stripped mixture of compounds containing both ether and amide linkages characteristic of the compounds of the present invention. The stripped mixture is tested and found to be useful as a dispersant additive in various lubricating compositions.

EXAMPLE Ill Example II is repeated except that maleic acid is used in place of maleic anhydride. Infrared analysis and molecular weight determinations of the autoclave mixture after toluene stripping confirm the presence of the characteristic compounds of the present invention. This stripped autoclave mixture is found to have utility as a dispersant additive in various lubricating compositions.

EXAMPLE IV it is difficult to overestimate the importance of providing the proper blend of lubricating fluid, dispersant composition and oxidation inhibitor. To illustrate, using a base fluid, e.g., a polyalkylene glycol diether polymer, the dispersant compositions of the present invention and an oxidation inhibitor, there is provided a I potential lifetime engine lubricant. The lubricating properties of the base fluid are not significantly diminished under normal operating conditions. However, over long periods of time, the base fluid may be oxidized to form volatile components which are discharged from the engine crankcase. An effective oxidation inhibitor may, therefore, be necessary to prevent too rapid decomposition of the base fluid resulting in the necessity for continual addition or replacement of lubricant. Sludge is formed in every internal combustion engine from combustion products, wear products, etc. It is essential that this sludge be maintained in the lubricant and carried to an effective filter. Therefore, an effective dispersant composition additive is required to provide an essentially homogeneous circulating lubricant in which the sludge forming materials are maintained in dispersion. As the homogeneous lubricant is circulated through the oil filter, the sludge components are removed and the clean lubricating fluid is returned to the crankcase. Except for occasional addition of lubricating fluid, no additional attention need be given to a vehicle's engine lubricating system. The convenience and economy of this type of fluid are immediately apparent.

The lubricating compositions of this invention, the dispersant compositions, and the process for preparing these products have been set forth in rather specific terms to aid those skilled in the art to understand and to practice the invention. Departures from the specific disclosure will be made by those skilled in the art based upon the principles and teachings herein and such variations may be made without departing from the spirit and scope of the invention, as defined in the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A compound having the following structures:

R R l s y IR -l-OCH CH 4 o c c N +12 ma a wherein each R and R is independently selected from the group consisting of hydrogen and monovalent hydrocarbonaceous radicals containing less than about carbon atoms, each R and Ris independently selected from the group consisting of hydrogen and alkyl containing from 1 to about 10 carbon atoms, each R is independently selected from the group consisting of divalent hydrocarbonaceous radicals containing from 1 to about 3 carbon atoms, n is a positive integer in the range from about I to about 100 and m is a positive integer from about 1 to about 10.

2. The compound of claim 1 wherein each R and R is independently selected from the group consisting of hydrogen and alkyl containing from 1 to about 6 carbon atoms, each R and R is independently selected from the group consisting of hydrogen and alkyl containing from 1 to about 4 carbon atoms, all R s are the same and selected from the group consisting of ethylene and propylene, n is from about 10 to about 100, and n is at least about 3 times m.

3. The compound of claim 2 wherein R and R are both hydrogen, all R s and Rs are methyl, and all R s are ethylene.

4. The compound of claim 3 wherein n is from about 10 to about 40 and is about 5 to about 15 times m.

5. A method for, making a dispersant composition which comprises: 7 i

1. contacting a polyalkylene glycol polymer with a maleic compound in an amount of from about 0.1 mole to about 3 moles of glycol polymer per mole of maleic compound at conditions sufficient to etherify at least a portion of said maleic compound at the carbon-carbon double bond, said polyalkylene glycol polymer being selected from the group consisting of R eocH ens- OH and mixtures thereof, wherein each R and R is independently selected from the group consisting of hydrogen and alkyl containing from 1 to about 10 carbon atoms and n is a positive integer from 1 to about 100, said maleic compound being selected from the group consisting of R c c R C-C-OH R2C-C and mixtures thereof, wherein each R is independently selected from the group consisting of divalent hydrocarbonaceous radicals containing from 1 to about 3 carbon atoms, and m is a positive integer from 1 to about 10.

6. The method of claim 5 wherein the contacting of step (1) takes place at pressures in the range from about 0.] atmosphere to about 50 atmospheres and temperatures in the range from about 25C. to about 250C. for a period of time from about 1 hour to about 500 hours, and the contacting of step (2) takes place at pressures in the range from about 0.1 atmosphere to about 50 atmospheres and at temperatures in the range from about 50C. to about 300C. for a period of time from about 1 hour to about 100 hours.

7. The method of claim 6 wherein R and R are inde pendently selected from the group consisting of hydrogen and alkyl containing from 1 to about 6 carbon atoms, each R and R is selected from the group consisting of hydrogen and alkyl containing from 1 to about 4 atoms, n is from about to about 100, all R s are the same and n is at least about 3 times m.

8. The method of claim 7 wherein from about 0.5 mole to about 1.5 moles of glycol polymer is present per mole of maleic compound and from about 0.5 mole to about 1.5 moles of polyamine is present per mole of maleic compound contacted in step (1).

9. The method of claim 8 wherein the contacting of step (1) takes place at pressures in the range from about 1 atmosphere to about 10 atmospheres and temperatures in the range from about 150C. to about 225C. for a period of time from about 10 hours to about 200 hours, and the contacting of step 2) takes place at pressures in the range from about 1 atmosphere to about 10 atmospheres and temperatures in the range from about C. to about 225C. for a period of time from about 10 hours to about 50 hours.

10. The method of claim 9 wherein R and R are both hydrogen, all R s and R s are methyl, all R s are ethylene, n is from about 10 to about 40 and n is from about 5 to about 15 times m.

11. The method of claim 6 wherein steps (1) and (2) take place in the presence of an essentially inert solvent.

12. The method of claim 10 wherein steps (1) and (2) take place in the presence of an essentially inert solvent. 

1. A COMPOUND HAVING THE FOLLOWING STRUCTURES:
 2. contacting said etherified product with a polyalkylene polyamine in an amount from about 0.1 mole to about 3 mole of polyamine per mole of maleic compound contacted in step (1) at conditions sufficient to react at least a portion of said etherified product with said polyamine to form said dispersant composition, said polyalkylene polyamine being selected from the group consisting of
 2. The compound of claim 1 wherein each R1 and R2 is independently selected from the group consisting of hydrogen and alkyl containing from 1 to about 6 carbon atoms, each R3 and R4 is independently selected from the group consisting of hydrogen and alkyl containing from 1 to about 4 carbon atoms, all R5''s are the same and selected from the group consisting of ethylene and propylene, n is from about 10 to about 100, and n is at least about 3 times m.
 3. The compound of claim 2 wherein R1 and R2 are both hydrogen, all R3''s and R4''s are methyl, and all R5''s are ethylene.
 4. The compound of claim 3 wherein n is from about 10 to about 40 and is about 5 to about 15 times m.
 5. A method for making a dispersant composition which comprises:
 6. The method of claim 5 wherein the contacting of step (1) takes place at pressures in the range from about 0.1 atmosphere to about 50 atmospheres and temperatures in the range from about 25*C. to about 250*C. for a period of time from about 1 hour to about 500 hours, and the contacting of step (2) takes place at pressures in the range from about 0.1 atmosphere to about 50 atmospheres and at temperatures in the range from about 50*C. to about 300*C. for a period of time from about 1 hour to about 100 hours.
 7. The method of claim 6 wherein R1 and R2 are independently selected from the group consisting of hydrogen and alkyl containing from 1 to about 6 carbon atoms, each R3 and R4 is selected from the group consisting of hydrogen and alkyl containing from 1 to about 4 atoms, n is from about 10 to about 100, all R5''s are the same and n is at least about 3 times m.
 8. The method of claim 7 wherein from about 0.5 mole to about 1.5 moles of glycol polymer is present per mole of maleic compound and from about 0.5 mole to about 1.5 moles of polyamine is present per mole of maleic compound contacted in step (1).
 9. The method of claim 8 wherein the contacting of step (1) takes place at pressures in the range from about 1 atmosphere to about 10 atmospheres and temperatures in the range from about 150*C. to about 225*C. for a period of time from about 10 hours to about 200 hours, and the contacting of step (2) takes place at pressures in the range from about 1 atmosphere to about 10 atmospheres and temperatures in the range from about 100*C. to about 225*C. for a period of time from about 10 hours to about 50 hours.
 10. The method of claim 9 wherein R1 and R2 are both hydrogen, all R3''s and R4''s are methyl, all R5''s are ethylene, n is from about 10 to about 40 and n is from about 5 to about 15 times m.
 11. The method of claim 6 wherein steps (1) and (2) take place in the presence of an essentially inert solvent.
 12. The method of claim 10 wherein steps (1) and (2) take place in the presence of an essentially inert solvent. 